Shortly before being named prime minister, Mr Marcinkiewicz told the Polish edition of Newsweek magazine that homosexuality was "unnatural". Since gaining office he has abolished the Polish equality watchdog.

Although Mr Marcinkiewicz, of the conservative Law and Justice party, said he would not "judge a person differently" if they were homosexual, according to Reuters in October he said it was "unnatural" and they must not "infect others" with their homosexuality.

Another member of his party, the Warsaw mayor, Lech Kaczynski, banned this year's Gay Pride march in the capital, leading to activists who defied the order being pelted with eggs and stones by anti-gay counter-protestors.

London MEP Jean Lambert, who is a member of the European parliament's gay and lesbian rights group, said: "Mr Marcinkiewicz's actions following his election have caused a big step backwards in the development of Poland as a democratic country. I am outraged that anyone, especially an elected prime minister, would tolerate and actually promote homophobia. By not condemning homophobic acts Poland will be in danger of entering into a cycle of violence."

Gay rights activist Peter Tatchell will later lead a protest outside the London thinktank Chatham House, where Mr Marcinkiewicz is due to give a speech.